code: def test_rgba():
      rgba = path.join(path.dirname(__file__), "data", "rgba.png")
      rgba = freeimage.imread(rgba)
      assert np.all(np.diff(rgba[:, :, 3].mean(1)) < 0)
  
file_path: mahotas/mahotas/tests/test_freeimage.py
imports: import numpy
  from os import path
label_desc: Use image node_id 3 for calling a global function with example usage: test_rgba() without return types